What we have here are fake corn cobs, made of plastic. They are sliced
exactly in half down their parting line, and then nailed to a piece of
melamine shelving. A chemical called PVA (poly vinyl alcohol) has been
brushed on to act as a mold release for the fiberglass resin.
The whole idea here is to make a pattern for an aluminum corn-cob
making mold. The finished aluminum piece that this pattern will produce
will be used for casting epoxy replicas of...you guessed it, corn cobs.
It's a "mold to make a mold" project! |
Plastic corn halves coated with release
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| On an earlier attempt, I had used just resin and cloth against the
corn-kernel surface. This resulted in a lot of trapped air, and big
ugly voids. So as you can see in the picture, I smeared the cobs with
bondo to help fill in between the kernels to make a better imprint. It
worked. |
Buttered with bondo for good surface reproduction
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| Now, on top of the bondo, I'm putting about 3 layers of fiberglass
cloth and resin, tucking it neatly down between the cobs. I used
aluminum duct sealer tape to form a dam to hold in the resin, which I
poured to about a quarter inch (7mm) thick. |
Fiberglass cloth and resin coating
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| The PVA mold release now officially has my utmost respect. The mold
pulled free of the melamine, and the corn cobs pulled very neatly out
of the Bondoed cavities. |
Resin and bondo cured, corn cobs removed
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| I used the bottom of a paint can to draw the radii of the corners, then
cut out the whole pattern with a band saw. The tab at the right end
will be drilled and used for hanging the corn molds on a pegboard hook
or something. |
Trimmed and ready for touchup
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| There were still a few air bubbles in the resin, so I filled them in with Bondo putty as well, then sanded them down smooth. |
Blemishes filled, ready for paint
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I always paint my patterns with the obligatory "Dan's
Workshop-dot-com-gray" paint (most accurately color matched of course),
acquired from my local Home Depot.
Painting the patterns helps to spot any blemishes that might have
gotten missed. It also makes a nice slick finish for the molding sand
to release from. Stay tuned! |
Finished pattern, ready for the molding bench
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